I am currently playing with Elastic Stack and APM. I have installed ElasticSearch 6.4.3 and APM-Server 6.5.0 without errors.
On a tomcat 8.0.x I added the following options:
-javaagent:/home/user/apm-server-6.5.0-linux-x86_64/elastic-apm-agent-1.0.0.jar
-Delastic.apm.service_name=DEV-TOMCAT
-Delastic.apm.application_packages=com.myPackage
-Delastic.apm.server_urls=http://127.0.0.1:8200"

I'm sorry you are having troubles with it. I have just tested pretty much all dbcp and dbcp2 versions but was not able to reproduce the problem.

Wolfram_Haussig:

org/apache/commons/dbcp/DelegatingStatement

That indicates that you are not using dbcp2 but dbcp because otherwise the class name would be org/apache/commons/dbcp2/DelegatingStatement (notice the dbcp2). But dbcp does not have a version 2.2.0. Could you recheck that again?

Thanks for the fast response. We are using Tomcat 8.0.51 running under openJDK 11 on "Red Hat Enterprise Linux Server release 6.10" - might that be the problem? We are currently evaluating running openJDK because of the oracle license change...

Could you try out dbcp 1.4? This version is compiled against Java 1.6 whereas dbcp 1.3 has been compiled against Java 1.4 which Byte Buddy (the bytecode manipulation framework we are using) does not support.